[tracing] Fix MemoryDumpManager periodic scheduler and improve tests

base/trace_event/memory_dump_manager.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_
 #define BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_
 
 #include <set>
 
 #include "base/atomicops.h"
@@ skipping 74 matching lines @@
   }
 
   // Returns a unique id for identifying the processes. The id can be
   // retrieved by child processes only when tracing is enabled. This is
   // intended to express cross-process sharing of memory dumps on the
   // child-process side, without having to know its own child process id.
   uint64 GetTracingProcessId() const;
 
   // Returns the name for a the allocated_objects dump. Use this to declare
   // suballocator dumps from other dump providers.
-  // It should not return nullptr after the manager has been initialized.
+  // It will return nullptr if there is no dump provider for the system
+  // allocator registered (which is currently the case for Mac OS).
   const char* system_allocator_pool_name() const {
-    return system_allocator_pool_name_;
+    return kSystemAllocatorPoolName;
   };
 
   // Tells the initialization phase to skip scheduling periodic memory dumps.
   void DisablePeriodicDumpsForTesting() {
     disable_periodic_dumps_for_testing_ = true;
   }
 
  private:
   friend struct DefaultDeleter<MemoryDumpManager>;  // For the testing instance.
   friend struct DefaultSingletonTraits<MemoryDumpManager>;
@@ skipping 59 matching lines @@
     // The thread on which FinalizeDumpAndAddToTrace() (and hence |callback|)
     // should be invoked. This is the thread on which the initial
     // CreateProcessDump() request was called.
     const scoped_refptr<SingleThreadTaskRunner> task_runner;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(ProcessMemoryDumpAsyncState);
   };
 
   static const int kMaxConsecutiveFailuresCount;
+  static const char* const kSystemAllocatorPoolName;
 
   MemoryDumpManager();
   ~MemoryDumpManager() override;
 
   static void SetInstanceForTesting(MemoryDumpManager* instance);
   static void FinalizeDumpAndAddToTrace(
       scoped_ptr<ProcessMemoryDumpAsyncState> pmd_async_state);
   static void AbortDumpLocked(MemoryDumpCallback callback,
                               scoped_refptr<SingleThreadTaskRunner> task_runner,
                               uint64 dump_guid);
@@ skipping 27 matching lines @@
   // dump_providers_enabled_ list) when tracing is not enabled.
   subtle::AtomicWord memory_tracing_enabled_;
 
   // For time-triggered periodic dumps.
   RepeatingTimer<MemoryDumpManager> periodic_dump_timer_;
 
   // The unique id of the child process. This is created only for tracing and is
   // expected to be valid only when tracing is enabled.
   uint64 tracing_process_id_;
 
-  // Name of the allocated_objects dump.
-  const char* system_allocator_pool_name_;
-
   // Skips the auto-registration of the core dumpers during Initialize().
   bool skip_core_dumpers_auto_registration_for_testing_;
 
   // When true, the initialization phase does not start the periodic memory
   // dumps.
   // TODO(primiano): This should go into TraceConfig. https://goo.gl/5Hj3o0.
   bool disable_periodic_dumps_for_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpManager);
 };
@@ skipping 23 matching lines @@
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpManagerDelegate);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_